This invention pertains to an operator for a casement-type window utilizing a pair of operator arms, both of which are rotatably mounted and with one arm engageable with the sash at a distance from the mounting edge of the sash to impart a rotational force thereto and the other operator arm connected to the sash adjacent the mounting edge thereof through a connecting link to exert a force acting in a direction generally parallel to the path of linear movement of the sash edge whereby the two arms work together and either the rotational force-applying arm or the linear force-applying arm may be effective, dependent upon which arm instantaneously encounters the least resistance in opening or closing of the sash.
A window of the general type to which the invention disclosed herein relates is shown in Gill U.S. Pat. No. 2,948,027. In such a window, the sash is mounted adjacent one edge at the top and bottom on slider structure including a slider movable in a guide track whereby said edge of the sash has both combined linear and pivotal movements along with pivotal movement of the sash. A constraining link is connected between the sash and window frame for guiding the sash movement.
Many different structures are known for a casement-type window operator wherein a manually operated pivotal operating arm is either directly or indirectly connected to the window sash for causing opening and closing movement thereof. The sash-mounting structure including the slider structure and the constraining link prescribe a certain timing between the velocity of the slider moving along a straight line path and the angular velocity of the sash which is hard to match with the conventional pivotal operating arm. Examples of conventional operator structures using a manually operated pivotal operating arm are shown in Reynaud U.S. Pat. No. 3,085,299 and Evers et al. U.S. Pat. No. 3,438,151.